Al doping for tuning magnetic and optical response of MgO monolayers

Abstract

Theoretical calculations are performed to study electronic, magnetic and optical properties of Al doped graphene-like MgO monolayers with impurity contents of 6.25 % and 12.5 %. Doping of Al has been considered not only as pure substitution and adsorption but also combination of these two. Al prefers Mg and O sites for pure substitution and adsorption, respectively. The substituted monolayers are planar, while adsorption of Al gives a buckling feature to the MgO plane. The impurity atoms induce magnetism in the host material irrespective of the type and site of doping, exceptionally when two consecutive sites are substituted with Al atoms. Semiconductor to metallic switching is observed in MgO monolayers for almost all of the doping configurations with Al substitution. On the other hand, Al adsorption results in reduced energy band gap values of pristine MgO monolayer due to the appearance of impurity states near the Fermi level. Consequently, the optical response of MgO monolayer gets tuned in presence of Al doping and accordingly becomes optically active for a wide spectral range starting from infrared to UV region in the electromagnetic spectrum. Notably, the system with consecutively adsorbed Al atoms is found to possess the maximum optical absorption in the Visible energy range. Therefore, nonmagnetic and UV optical characteristic of pristine MgO monolayer can be moderated through proficient decoration of Al for achieving a desirable material for spintronic and optoelectronic applications.